Mechanisms of Powder Consolidation (1)

Mechanisms of Powder Consolidation Based on Compact Porosity, Surface Area, and Strength: 

Mechanisms of Powder Consolidation Based on Compact Porosity, Surface Area, and Strength By: Professor Adi I. Arida Faculty of Pharmacy - Philadelphia University

PowerPoint Presentation: 

Whether consolidation of a powder bed under deformation or fragmentation, there will be some change in surface area. Then, as the particles assume an even closer relationship, this too will cause surface area changes. It follows that surface area studies may provide important information about the extent and mechanisms of particle consolidation

Each solid or mixture was subjected to the following:: 

Each solid or mixture was subjected to the following: Establishment of the relationships between compression pressure and tablet's specific surface area, and tablet tensile strength. In addition, relationships between tensile strength and porosity, tensile strength and surface area were established. The reason for the establishment of these relationships is trying to link between the specific surface area of the tablet and its consolidation mechanism, i.e. trying to identify whether the binding capacity of a tablet is related to its surface area or not. The effect of lubricant concentration on tablet properties was investigated.

Two factors could be regarded as primary factors for the tensile strength of pharmaceutical compacts:: 

Two factors could be regarded as primary factors for the tensile strength of pharmaceutical compacts: The strength of the interparticulate bonds. The surface area over which these bonds are active.

Indirect factors (secondary factors) have been studied and used for correlations with tablet strength: 

Indirect factors (secondary factors) have been studied and used for correlations with tablet strength The tensile strength of tablets depends on several such secondary factors, i.e. particle shape, surface texture, particle size and crystal structure. The bonding mechanisms co- or adhering particles together in compression of dry powders include three types: solid bridges (sintering, melting, crystallization, chemical reactions and hardened binders). Distance attraction forces (intermolecular forces). Mechanical interlocking (between irregularly shaped particles).

RICE STARCH: 

RICE STARCH

RICE STARCH: 

RICE STARCH

RICE STARCH: 

RICE STARCH

RICE STARCH: 

RICE STARCH

Comparative plots of pressure (MPa) versus specific surface area (m2/g) for tablets compressed from four excipients, using 0.5% magnesium stearate: 

Comparative plots of pressure (MPa) versus specific surface area (m 2 /g) for tablets compressed from four excipients, using 0.5% magnesium stearate

Comparative plots of tensile strength (MPa) versus compression pressure (MPa) for tablets compressed from four excipients, using 0.5% magnesium stearate: 

Comparative plots of tensile strength (MPa) versus compression pressure (MPa) for tablets compressed from four excipients, using 0.5% magnesium stearate

Comparative plots of the relationship between tablet tensile strength (MPa) and porosity for tablets compressed from four excipients, using 0.5% magnesium stearate: 

Comparative plots of the relationship between tablet tensile strength (MPa) and porosity for tablets compressed from four excipients, using 0.5% magnesium stearate

Comparative plots of specific surface area (m2/g) versus tensile strength (MPa) for tablets compressed from four excipients, using 0.5% magnesium stearate: 

Comparative plots of specific surface area (m 2 /g) versus tensile strength (MPa) for tablets compressed from four excipients, using 0.5% magnesium stearate

Tensile strength (MPa) at zero porosity for tablets compressed from four excipients: 

Tensile strength (MPa) at zero porosity for tablets compressed from four excipients Tensile strength (MPa) at zero porosity ‡ Tensile strength (MPa) at zero porosity † Powder 15 22 Rice starch ---- 9 # Avicel PH102 7 8 Zeparox 13 13 Emcompress † Lubricant concentration is 0.5% (w/w%). ‡ Lubricant concentration is 1.0% (w/w%). # No lubricant is used.

Factors playing a role in the consolidation mechanisms of rice starch are: : 

Factors playing a role in the consolidation mechanisms of rice starch are: The surface area, weak distance forces and solid bridges (when using low concentration of magnesium stearate; 0.5%). While if high concentration of magnesium stearate is used (1.0%), only the weak distance forces and solid bridges will play a role in the consolidation mechanism of rice starch

Factors playing a role in the consolidation mechanisms of Avicel PH102 are: : 

Factors playing a role in the consolidation mechanisms of Avicel PH102 are: The surface area. Distance forces (hydrogen bonds). Mechanical interlocking.

Factors playing a role in the consolidation mechanisms of Zeparox (Spray dried lactose) are: : 

Factors playing a role in the consolidation mechanisms of Zeparox (Spray dried lactose) are: Weak distance forces.

Factors playing a role in the consolidation mechanisms of Emcompress are:: 

Factors playing a role in the consolidation mechanisms of Emcompress are: Weak distance forces. Mechanical interlocking.

Notice: 

Notice According to the fact that rice starch (with 0.5% magnesium stearate) and Avicel PH102 (with no lubricant) differ only in their third type of bonding, this would affirm that the solid bridges are stronger than the mechanical interlocking forces